Reader Comments (28)

... the conferences very FIRST speaker is "Professor Steve Howdle, University of NottinghamPolymers and supercritical carbon dioxide"... and the THIRD speaker "Professor Vladimir Popov, Russian Academy of Sciences, RussiaSupercritical carbon dioxide: green solvent for pharmaceutical applications"

"The combination of gas-like and liquid-like properties makes supercritical carbon dioxide (sc-CO2) a unique processing medium for preparation of polymer materials containing bioactive species, primarily because no solvent residues would remain in the final product. "

Green chemistry was starting to become trendy when I was at university in the mid 80s. Since many solvents are pretty nasty things and used in quite large quantities this seems like a very good thing. Supercritical CO2 was the wonderfluid back then, and it looks like not much has changed.

"Green, sustainable, low carbon, zero carbon, not made from nasty controversial chemicals that are killing the poor feverish planet...."..take your pick and please think of the grandchildren while you're doing it :)

Would the manufacture of super critical CO2, be a 'solution' for the problem of where to store the carbon captured rom power station flue pipes, or does CO2's designation as Public Enemy No 1 override genuine health concerns as identified by M Courtney above.

The term "supercritical" has strong emotive effects on undergraduate chemistry students, some of whom carry that burden into their careers, and Royal Society meetings. As M. Courtney and Jonathan Jones point out, this meeting is apparently to discuss newer variants of very old ideas, many times proven impractical. It looks all quite boring, and we can all calm down.

"Would the manufacture of super critical CO2, be a 'solution' for the problem of where to store the carbon captured rom power station flue pipes"

The CO2 to be stored in CCS schemes will by physical necessity be supercritical given the pressures and temperatures. And supercritical CO2 really is a quite remarkably good solvent for virtually anything organic. So we are going to pump many billion tons of a very powerful solvent under extremely high pressure into imperfectly known rock formations.

What could possibly go wrong?

And the pressure requirement is basically why supercritical CO2 has been slow to catch on. The temperature (>304 K) is usually not a problem, but the minimum pressure is 7.4 MPa (c. 1075 psi) which is not trivial.

tty, thanks for that. By the time pressures have reached 1000psi, things are already in the 'dangerously interesting' category.

So to use sc CO2 as a solvent involves pressure vessels to contain the object, aswell as the sc CO2. It isn't going to be on Tesco's shelves in an aerosol can, but would be a brilliant oven cleaner otherwise. Similarly, dry cleaning solvents are not going to vapourise in an odourless manner either.

"But most current solvents are carcinogenic." Oh, yeah? What sort of company in industry uses them with all the regulatory and legal problems. The companies I worked for would not use anything as toxic as that sold over the counter at hardware stores. Nor "green" products - it is over 20 years since mixed cresols or 'cresylic acid' was removed because it was only used (rarely) with full isolation gear. Yet it is sold as a toilet disinfectant and GREEN - in use for 100 years (coal tar liquid).

Re supercritical solvents:The best known use is extracting caffeine with sc CO2 to make "caffeine free" coffee. CO2 replaced epiChloroHydrin used originally because that was found to be carcinogenic.The next 'best thing' might be methane. It is supercritical at lower temperature and pressure.

The Royal Society of Chemistry has actually been fairly sound on our favourite subject (I am glad to say, as a Chemistry graduate myself) and has generally not been overwhelmed by the AGW blob - probably because chemists actually understand a few of the principles involved and tend not to pay much attention to ignoramuses leading forth.

The meeting under discussion looks rather interesting, but it's a long time since I did any chemistry so I guess I won't be going...

@Graeme No.3: Agreed. It constantly amazes me that you can still buy caustic soda pellets in B&Q. I guess they have no idea how dangerous it is in the wrong hands, or perhaps they're so blinkered by the terrorism panic that anything non-flammable just doesn't get looked at. Thank goodness - because it's useful stuff.

I agree with Andrew Duffin, chemists have largely maintained their integrity and just get on with developing products to benefit mankind, which brings me on to the physicists and biologists! What is wrong with them, at least the ones that become BBC presenters and heads of the RS?

I suggest a compulsory 5-year re-education programme in chemistry, for those with obsessive planet-saving-and-self-promotion syndrome.

"Are the greens after the chemists now or have they been infiltrated already?"

The greens started with the chemists. The greens are anti-chemists. That's one of the reasons chemists are less susceptible than most to green hogwash.

That aside, supercritical fluids (CO2 and water in particular) are not much new, as others mentioned above. It is generally likely to remain a niche technology because of the engineering considerations.

While browsing the shelves of Carrfour in France for some toilet cleaner, I found largish bottles of hydrochloric acid for use as a patio cleaner. I wonder if B&Q could be persuaded to stock some of that.

The hazards associated with CO2 in the brewing industry are well known, yet people still die needlessly every year in tragic and completely avoidable accidents in breweries. Just last year in Germany, which has a good safety record, two workers died in separate incidents at the same brewery.

People at Lake Nyos were also affected, CO2 is nasty stuff in certain circumstances, although pretty harmless the rest of the time,

Lake Nyos suddenly emitted a large cloud of CO2, which suffocated 1,700 people and 3,500 livestock in nearby towns and villages.[2][3] Though not completely unprecedented, it was the first known large-scale asphyxiation caused by a natural event. To prevent a recurrence, a degassing tube that siphons water from the bottom layers of water to the top allowing the carbon dioxide to leak in safe quantities was installed in 2001, and two additional tubes were installed in 2011.

Environmentalists now love bird and bat chomping windmills, so I reckon they will suddenly develop a deep attachment to battery acid, as batteries are key to converting renewibles (sic) from a joke to a whatever.

My theory for why chemists are mostly sensible people: most of them become real world product developers or get other real jobs. Many physicists become engineers, another sensible bunch. That just leaves the academic physicists and biologists as a self selecting group of oddballs who either can't or won't get real jobs.

Mike Courtenay,If a solvent was a known carcinogen for humans, it would be on official lists. The substance benzene is on that list. From memory, carbon tetrachloride is also there. That is all. There are only 30 or so items on the list. Every liquid is a 'solvent'. Every case of cancer involves abnormal chemicals.Older Chemists - I am one - trends not to arm wave. We try to be more case-specfic.The present wave of green chemophobia is disgusting and insulting. It has essentally no scientific basis.Geoff.

Greens have hated chemists far longer that fossil fuel companies. Chemistry companies did a lot of things to the environment that we now recognize we pretty stupid, because they didn't have to pay the cost of safely disposing their waste streams. That era is now long gone in the developed world. Now chemists are looking for new processes that produce less waste, but businesses usually commercialize only those that reduce total cost. Otherwise the waste (and jobs) move to China.

The biggest green obscenity these days arises from promoting the belief that "natural" is good and man-made is bad. All living things are food for other living things. Plants and bacteria can't escape by running away or defending themselves physically. They rely on chemical warfare: antibiotics, poisons, bitter flavors, etc (:<)). I recently bought a product to discourage moles from eating my plants. Looking at the label more carefully, I read that it came from castor beans - the source of ricin used in chemical warfare. Since it is a "natural product", it wasn't regulated or approved by the EPA. (I returned the product.) No one knows if the natural products used on organic farms are safe, because they aren't tested. We know what's in GMO foods and they are tested for safety. No one knows what active ingredients are disease resistant crops bred by conventional methods. None of the crops we eat are "natural"; they are all the result of breeding by man.

Frank,You are generalising too much and too negatively.You will tend to remember highlighted chemical problems from the past, while tending to forget whether they were large and frequent, or merely annoying pimples on the bum of a huge, beneficial industry.More oftern, it is the latter.The evil that men do lives after them.Example. In my employer's company, we inherited by takeover a site that had been levelled after decades operating as a car battery recycle plant. The cleanup has been poor and Pb levels in the soil were about 1/20 of typical Pb mine levels. We were hit with a public greenie hate program and EPA demands for a very large number of $. The do-gooders closed ears to suggestions that the past social good was great - imagine how many inquisitive children were saved from playing with the sulphuric acid in all those discarded batteries in back yards instead of returns to the recycle plant. One of our corporate solcitors suggested we make the site into a cemetary where coffins lined with Pd were permitted.You see, it is oftern a matter of compromise, of putting problems into scientific and social perspectives.That is why, over history, people with specialidt knowledge tended to evolve into groups.p that we now call companies. The companies respond to the lure of the $, but the many better ones also respond to demands for a better society. We call that progress.Greenies think that they cause progress. Unfortunately, their knowledge of real world problems and solutions is next to zero.Indeed, green blather was an expensive distraction to my company's progress. I cannot recall the negative ignorances ever produced significant social gains.Their good will be interred within their bones?

You are right, but almost all blog comments (which must be short) over-generalize and are either too negative or too positive. I should be more cautious.

When I said that some things done by chemistry companies in the past were pretty stupid, that didn't mean that valuable products or services weren't being produced when the environment was damaged. And some of that stupidity is only apparent with 20:20 hindsight. In either case, the cost of properly disposing waste streams should have been included in the price of the valuable products and services that were being produced. Despite our experiences, today's China demonstrates that it is very hard for developing economies (which we once were) to spend money protecting the environment - when reducing poverty is the primary consideration. I'm sure that GHGs are at the bottom of China's long list of environmental problems.

As for the lead in the soil on your company's property, I suspect the real problem is the possibility that it could migrate into ground water or be blown to another location. Creating a cemetery for leaded coffins doesn't help with these problems - and I doubt leaded coffins are superior to environmentally safer alternatives. If the lead concentrates in grass, the grass clippings from a cemetery could become hazardous waste. (I don't know if phytoremediation is practical yet.) If the lead isn't going to migrate from your property to somewhere else (at a rate that poses a real hazard to your neighbors) or if you can prevent migration, there really isn't a good reason for the government to force you to clean up the site. Unfortunately, government bureaucrats: only get in trouble if they aren't careful enough, abide by the precautionary principle, and aren't personally required to pay any unnecessary costs they create. (Like you, I have some experience with the possibility of contamination.)

Frank,I hope I was not too hard on you. We seem to have common ground.Just to round this off, the remediation considered for the Pb site started with a metre of good soil over the top.The coffin suggestion was not serious, merely intended to show that some people are select in what they demonise, like Pb from battery recycle is hate and Pb metal, lots of it, buried in a coffin draws no hate.Then, no credit for saving kids exposed to sulphuric acid.Double standards are alive and well.We actually took the EPA to Court claiming that the remediation plan they asked of us was impossible to execute reasonably. The Judge agreed with us and the EPA pulled its horns in and went off to pester other demons.

My personal application of chemistry assisted in world markets obtaining enough uranium to offset coal combustion to the tune of billions of tonnes of CO2 potential and actual, if that is in reality a benefit. The uranium certainly is a benefit, unless you are green. For that, none of our team ever received a thank you from anyone. Such is the power of negative propaganda.Keep well Geoff.

Geoff: I'm not thin-skinned and you are one of the shrewder comments on climate science. Fire away.

As best I can tell, we need more people bringing useful products into the marketplace, whether or not the greens approve. They used to be called "capitalist exploiters of the masses" (and still are by the left). Now they are a best hope for producing full employment, driving up wages (minimizing "income inequality"), and reducing our debt and unfunded liabilities.